Malphite. He's in the meta right now, he's cheap to buy, and he does all the things junglers need to do.

warwick is the safest jungle

you can kill everything with no runes/items/masteries basically

another easy jungler is amumu or fiddlesticks

Ww is good to start off with. He pretty much cant die with his q and w to heal. Oh and cant forget the passive.

id go with malph, my second ranked game I played him as we needed a jungle, and I was the last to pick, when I explained I was new to jungle earlier they said it was ok, when it was my pick to do malph and be a tanky jungle. I did that and after that I am now going to try him in jungle a lot more as it was the most fun I ever had with malph as well as one of the most fun times I had in league as it is.

I started with warwick back when a jungler was a funny idea

Warwick and Nunu can jungle a full clear bare-naked with no potions, it's EASY.

Amumu can't do that, but it's still pretty easy, and he's a very nice champ overall.

Maokai is my favorite and his fans ganks are strong.. Go to solomid and look up a guide for him. It's real ez and has a vid to show you how.

My first jungler was Shyvana. Her w makes her a fast clearer, and she can be built to take or give lots of damage. If you aren't familiar with her set, though, I'd say try Nocturne. His passive makes him a fast clearer as well, and he can stay in the jungle longer than Shyvana can - he can clear it a couple times without even using more than one or two pots. His set is also made for fast and clean ganks.

This is honestly a very complicated question. It really depends on what role you intend to fulfill as a jungler, namely whether you want to be a tanky champ with tons of cc or a glass cannon such as shaco. The prob with playing a tanky champ is that it means that if you are playing solo que you are relying on your teammates to carry you to victory. If you have friends to play with though, a tanky jungler is easier to play. so my suggestions are as follows:

Solo Que

Darius, WW, Trynd, Olaf, Udyr

With friends

Udyr, WW(still good choices), Shen, Malphite,

DO NOT TRY NAUT WITHOUT A LOT OF PRACTICE. He requires skill and aslo familiarity with jungling. I also highly recommend Udyr over WW.